Abstract
A novel approach to heterogenization of catalytic molecules is demonstrated using the nanoscale graphitic step edges inside hollow graphitized carbon nanofibers (GNFs). The presence of the fullerene C60 moiety within a fullerene–salen CuII complex is essential for anchoring the catalyst within the GNF nanoreactor as demonstrated by comparison to the analogous catalyst complex without the fullerene group. The presence of the catalyst at the step edges of the GNFs is confirmed by high-resolution transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDX) with ultraviolet/visible (UV/vis) spectroscopy, demonstrating only negligible (ca. 3%) desorption of the fullerene–salen CuII complex from the GNFs into solution under typical reaction conditions. The catalyst immobilized in GNFs shows good catalytic activity and selectivity toward styrene epoxidation, comparable to the analogous catalyst in solution. Moreover, the fullerene–salen CuII complex in GNFs demonstrates excellent stabili...
Highlights
The ability to separate and recycle the metal catalyst from reaction mixtures without excessive purification steps is crucial for sustainable transition-metal based catalysis.[1]
In this study we report a new methodology for heterogenisation of transition metal catalysts by tagging them with a fullerene group which allows reliable and site-specific anchoring inside graphitised carbon nanofibres (GNF) via strong van der Waals interactions between the fullerene cage and the internal graphitic step-edges of GNFs
The analogous fullerene-free complex 2 was prepared for comparison. [Cu(II)(salen)] complexes are known to catalyse epoxidation reactions of alkenes, and it has been demonstrated previously that a slight enhancement of the catalytic activity of the transition metal complex is observed upon addition of the fullerene cage due to the electron withdrawing nature of the carbon cage.[15]
Summary
The ability to separate and recycle the metal catalyst from reaction mixtures without excessive purification steps is crucial for sustainable transition-metal based catalysis.[1]. Hybridised carbon structures and is an excellent match for the preferential binding at graphitic step-edges rather than the flat terrace of the inner surface of the GNF support.[13] We demonstrate that non-covalent immobilisation of a fullerene-tagged [Cu(salen)] catalyst inside GNF nanoreactors can be used to form well-defined heterogeneous catalysts with molecules located in a very distinct, confined environment.
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